Heretofore, with respect to a resin-encapsulated semiconductor device, marking is made using a thermocurable or UV-curable special ink. However, in such a method, much time is taken for marking and curing and, in addition, the ink is not easy to handle.
Consequently, at present, marking with a YAG laser or a carbon dioxide laser is a mainstream. As compared with marking with ink, marking with a YAG laser or a carbon dioxide laser has various advantages in that it is excellent in operability and the working time can be significantly shortened.
However, in marking with a YAG laser or a carbon dioxide laser, the contrast between the marked part and the non-marked part is not sufficient and therefore the marking is not vivid. In addition, reading may often be difficult owing to yellowing to be caused by oxidation of the phenolic resin curing agent in the encapsulating resin.
Accordingly, various studies are being made for improving the laser marking performance of such an encapsulating resin composition for use for encapsulation of semiconductor devices, and for example, some techniques of using carbon black as a black pigment and specifically defining the range of the mean particle size thereof as well as the amount thereof to be added have been proposed (for example, see PTLs 1 to 3).
However, carbon black is electroconductive, and therefore, in the case where carbon black is applied to encapsulation of high-precision wiring in high-integration semiconductor devices in recent years, a risk of leakage (short circuit) may occur. For solving the problem, use of fullerenes almost free from a risk of leakage (short circuit) in place of carbon black has been proposed (for example, see PTL 4).